In order to acquire intellect one must need it. One loses it when it is no longer necessary.

Necessity is not an established fact, but an interpretation.

A good author possesses not only his own intellect, but also that of his friends.

All idealism is falsehood in the face of necessity

One hears but one does not seek; one takes -- one does not ask who gives; a thought flashes up like lightning, it comes of necessity and unfalteringly formed.

No small art is it to sleep: it is necessary for that purpose to keep awake all day.